1. Field of the Invention
The invention relates to moving media storage technology and, more particularly, to a method and apparatus for the recording of large blocks of rapidly arriving data and for the playback of such recordings.
2. Description of the Prior Art
Disk drives have been used in the computer industry for many years for the storage of data for later use. The economic factors in the industry have caused the development of a series of disk drives that have progressively been smaller and cheaper, and that have both more storage capacity and faster access times. Throughout their history, however, they have only had to deal with small blocks of data, or with blocks of data that arrived slowly enough to be subdivided. Thus the data could be stored in distinct sectors on distinct tracks on the disk. Furthermore, organizing the disk's storage capability in this fashion allows the retrieval and changing of any particular block of data.
In the above-referenced copending patent application, Ser. No. 06/256,411, of Armin Miller, et al., there is described a high resolution electronic camera with storage capability. The image at the focal plane of a lens is scanned in one direction by a linear photodiode array and in the orthogonal direction by relative motion of the linear array with respect to the lens. Since the linear array has about 2,000 photoactive elements, a scan of a standard 81/2".times.11" page results in over five million data points. Presently-available disk drives with this much storage capability are very much larger than the mechanism required to do the described scanning. An unconventional and unique disk drive would be required to keep the total package size reasonable.
The photodiode array converts photons to electrons. The gain of the device is specified in terms of output charge versus illumination level. This gain is directly proportional to the length of time allowed to collect the photon-generated electrons before presenting the collection at the output. Thus, the cycling of the linear array is crystal controlled and never varies. The mechanical scanning of the array across the image plane of the lens is similarly well controlled. The array must advance exactly one photodiode width for every cycling of the diodes of the array. Any variation in this will generate a magnification error as successive scans of the linear array are mechanically unexpectedly too close together, or too far apart. Thus, the rhythm of making an exposure, and recording it, is set by the camera and cannot be set by the recording disk drive. The conventional way to connect the camera to a disk would be to buffer the data flow from the camera so that sector identification codes and track jumps can be accommodated. Such a buffer would add to the cost, volume, and weight of the final product. The alternative was to invent a new and unique disk drive that had neither sectoring nor track jumping.
The removal of sectoring was relatively straightforward. There is no need to get at random sections of a block of data when the data comes in one integrated whole, like the output of an electronic camera. Thus, sectoring could be dropped without its function being picked up in some fashion elsewhere.
The removal of track jumping was complicated by several considerations. Some way of moving from one track to another is obviously necessary; the problem was to do it in a systematic fashion so that recording could continue without interruption and so that playback would be possible. The situation was further complicated by the necessity of using flexible disks, rather than hard disks, because their replacement costs are much lower. A person taking pictures effectively with a disk drive is going to be using a lot of disks, and they must be individually relatively inexpensive. The final complication was that, in order to get the required amount of data stored on a disk of reasonable size, the state-of-the-art of floppy-disk drives had to be improved by a factor of ten or twenty. This improvement was accomplished mainly through the invention of an improved mechanism that achieved greater track densities.
The above-referenced applications by Miller, et al. describes certain aspects of the data storage and retrieval problems described above, but only with respect to the development of a high-resolution camera with storage. No claims were made of the innovations that are unique and useful with respect to the general data storage and retrieval industry.
Accordingly, a primary object of this invention is to rapidly record a large block of data at low cost.
It is another object of this invention to increase greatly the storage capacity of floppy-disk drives.
It is a further object of this invention to record data onto a disk in a spiral format.
It is a yet further object of this invention to accomplish track following during the playback of data recorded on a spiral.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.